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"alt_text": "This animation illustrates the direct relationship between a pulsar's X-ray pulses and its quasi-periodic oscillation (QPO), a flickering signal that hovers around certain frequencies. The QPO is shown here as a bright patch near the inner edge of the disk of gas that feeds matter to the pulsar at the center, called SAX J1808. Guided by magnetic fields, gas streaming onto the neutron star forms bright hot spots. As the pulsar spins 401 times a second, telescopes detect X-ray pulses as these locations swing into view from Earth. When the QPO orbits more slowly than the pulsar’s spin, the neutron star’s magnetic field holds back flowing gas, dimming the X-ray pulses. But during an outburst, the inner edge of the disk is forced closer to the pulsar, resulting in a faster-moving QPO and compression of the pulsar's magnetic field. When the QPO matches or bests the pulsar’s spin, more gas streams onto the neutron star, and the pulses brighten. Gas may even flow directly onto the pulsar's equatorial region, producing extra hot spots. NASA’s Rossi X-ray Timing Explorer observed this relationship during outbursts in 2002, 2005, and 2008. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab",
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"alt_text": "This animation illustrates the direct relationship between a pulsar's X-ray pulses and its quasi-periodic oscillation (QPO), a flickering signal that hovers around certain frequencies. The QPO is shown here as a bright patch near the inner edge of the disk of gas that feeds matter to the pulsar at the center, called SAX J1808. Guided by magnetic fields, gas streaming onto the neutron star forms bright hot spots. As the pulsar spins 401 times a second, telescopes detect X-ray pulses as these locations swing into view from Earth. When the QPO orbits more slowly than the pulsar’s spin, the neutron star’s magnetic field holds back flowing gas, dimming the X-ray pulses. But during an outburst, the inner edge of the disk is forced closer to the pulsar, resulting in a faster-moving QPO and compression of the pulsar's magnetic field. When the QPO matches or bests the pulsar’s spin, more gas streams onto the neutron star, and the pulses brighten. Gas may even flow directly onto the pulsar's equatorial region, producing extra hot spots. NASA’s Rossi X-ray Timing Explorer observed this relationship during outbursts in 2002, 2005, and 2008. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab",
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"alt_text": "This animation illustrates the direct relationship between a pulsar's X-ray pulses and its quasi-periodic oscillation (QPO), a flickering signal that hovers around certain frequencies. The QPO is shown here as a bright patch near the inner edge of the disk of gas that feeds matter to the pulsar at the center, called SAX J1808. Guided by magnetic fields, gas streaming onto the neutron star forms bright hot spots. As the pulsar spins 401 times a second, telescopes detect X-ray pulses as these locations swing into view from Earth. When the QPO orbits more slowly than the pulsar’s spin, the neutron star’s magnetic field holds back flowing gas, dimming the X-ray pulses. But during an outburst, the inner edge of the disk is forced closer to the pulsar, resulting in a faster-moving QPO and compression of the pulsar's magnetic field. When the QPO matches or bests the pulsar’s spin, more gas streams onto the neutron star, and the pulses brighten. Gas may even flow directly onto the pulsar's equatorial region, producing extra hot spots. NASA’s Rossi X-ray Timing Explorer observed this relationship during outbursts in 2002, 2005, and 2008. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab",
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"alt_text": "This animation illustrates the direct relationship between a pulsar's X-ray pulses and its quasi-periodic oscillation (QPO), a flickering signal that hovers around certain frequencies. The QPO is shown here as a bright patch near the inner edge of the disk of gas that feeds matter to the pulsar at the center, called SAX J1808. Guided by magnetic fields, gas streaming onto the neutron star forms bright hot spots. As the pulsar spins 401 times a second, telescopes detect X-ray pulses as these locations swing into view from Earth. When the QPO orbits more slowly than the pulsar’s spin, the neutron star’s magnetic field holds back flowing gas, dimming the X-ray pulses. But during an outburst, the inner edge of the disk is forced closer to the pulsar, resulting in a faster-moving QPO and compression of the pulsar's magnetic field. When the QPO matches or bests the pulsar’s spin, more gas streams onto the neutron star, and the pulses brighten. Gas may even flow directly onto the pulsar's equatorial region, producing extra hot spots. NASA’s Rossi X-ray Timing Explorer observed this relationship during outbursts in 2002, 2005, and 2008. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab",
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"alt_text": "This animation illustrates the direct relationship between a pulsar's X-ray pulses and its quasi-periodic oscillation (QPO), a flickering signal that hovers around certain frequencies. The QPO is shown here as a bright patch near the inner edge of the disk of gas that feeds matter to the pulsar at the center, called SAX J1808. Guided by magnetic fields, gas streaming onto the neutron star forms bright hot spots. As the pulsar spins 401 times a second, telescopes detect X-ray pulses as these locations swing into view from Earth. When the QPO orbits more slowly than the pulsar’s spin, the neutron star’s magnetic field holds back flowing gas, dimming the X-ray pulses. But during an outburst, the inner edge of the disk is forced closer to the pulsar, resulting in a faster-moving QPO and compression of the pulsar's magnetic field. When the QPO matches or bests the pulsar’s spin, more gas streams onto the neutron star, and the pulses brighten. Gas may even flow directly onto the pulsar's equatorial region, producing extra hot spots. NASA’s Rossi X-ray Timing Explorer observed this relationship during outbursts in 2002, 2005, and 2008. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab",
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"alt_text": "This animation illustrates the direct relationship between a pulsar's X-ray pulses and its quasi-periodic oscillation (QPO), a flickering signal that hovers around certain frequencies. The QPO is shown here as a bright patch near the inner edge of the disk of gas that feeds matter to the pulsar at the center, called SAX J1808. Guided by magnetic fields, gas streaming onto the neutron star forms bright hot spots. As the pulsar spins 401 times a second, telescopes detect X-ray pulses as these locations swing into view from Earth. When the QPO orbits more slowly than the pulsar’s spin, the neutron star’s magnetic field holds back flowing gas, dimming the X-ray pulses. But during an outburst, the inner edge of the disk is forced closer to the pulsar, resulting in a faster-moving QPO and compression of the pulsar's magnetic field. When the QPO matches or bests the pulsar’s spin, more gas streams onto the neutron star, and the pulses brighten. Gas may even flow directly onto the pulsar's equatorial region, producing extra hot spots. NASA’s Rossi X-ray Timing Explorer observed this relationship during outbursts in 2002, 2005, and 2008. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab",
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"description": "For pulsars like SAX J1808.43658 (SAX J1808 for short), gas channeled onto the neutron star’s magnetic poles creates hot spots that produce intense X-rays. The pulsar spins 401 times a second, and orbiting X-ray telescopes detect strong pulses when these hot spots wheel into view from Earth.
But there's another signal as well — an X-ray flickering known as a quasi-periodic oscillation, or QPO, that hovers around certain frequencies. For SAX J1808, the QPO varies up to 700 times a second.
Observations from NASA's Rossi X-ray Timing Explorer (RXTE) have shown that the pulses and the QPO have a direct relationship, providing insight into the inner structure of the accretion disk. X-ray pulses from the hot spots shine twice as bright when the QPO frequency matches or is faster than the pulsar’s spin, and their brightness dims by the same amount when the QPO fluctuates more slowly than the pulsar’s rotation. RXTE observed these changes during outbursts in 2002, 2005, and 2008.
This result strongly suggests that the QPO is a region of especially hot plasma near the inner edge of the accretion disk and that its fluctuations trace its orbital motion. When the QPO orbits more slowly than the neutron star’s spin, the flow of matter onto the pulsar becomes inhibited by the pulsar’s magnetic field. During an outburst, the inner edge of the disk is forced closer to the pulsar, resulting in a faster-moving QPO and compression of the magnetic field. When the QPO matches or bests the pulsar’s spin, the flow of matter onto the neutron star is enhanced, with more gas reaching the magnetic poles to brighter pulses. During these episodes, matter may also flow directly onto the pulsar's equatorial regions (lateral accretion).",
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{
"id": 14209,
"url": "https://svs.gsfc.nasa.gov/14209/",
"page_type": "Produced Video",
"title": "NASA’s Compton Mission Glimpses Supersized Neutron Stars",
"description": "This simulation tracks the gravitational wave and density changes as two orbiting neutron stars crash together. Dark purple colors represent the lowest densities, while yellow-white shows the highest. An audible tone and a visual frequency scale (at left) track the steady rise in the frequency of gravitational waves as the neutron stars close. When the objects merge at 42 seconds, the gravitational waves suddenly jump to frequencies of thousands of hertz and bounce between two primary tones (quasiperiodic oscillations, or QPOs). The presence of these signals in such simulations led to the search and discovery of similar phenomena in the light emitted by short gamma-ray bursts.Credit: NASA's Goddard Space Flight Center and STAG Research Centre/Peter HammondComplete transcript available.Watch this video on the NASA Goddard YouTube channel.Visual description:On a black background with a faint gray grid, two multicolored blobs representing merging neutron stars circle and close. The colors indicate density. Yellow-white indicates the highest densities, at the centers of the objects. The colors change to orange and red at their periphery, with purple colors representing matter torn from and swirling with the neutron stars as they orbit. The grid shrinks as the camera pulls back to capture a wider view of the merger. A pale orange display at left shows the changing frequency of the gravitational waves generated, which is also indicated by the rising tone. As the merger occurs, the screen shows a spinning yellow blob at center immersed in a large cloud of magneta and purple debris. || Merger_Simulation_Annotated_Still_2.jpg (1920x1080) [180.7 KB] || 14209_Hypermassive_QPO_Simulation_Zoom_YOUTUBE_1080.webm (1920x1080) [12.1 MB] || 14209_Hypermassive_QPO_Simulation_Zoom_YOUTUBE_1080.mp4 (1920x1080) [129.3 MB] || 14209_Hypermassive_QPO_Simulation_Zoom_YOUTUBE_BEST_1080.mp4 (1920x1080) [161.8 MB] || 14209_NS_Merger_QPO_SRT_Captions.en_US.srt [1.6 KB] || 14209_NS_Merger_QPO_SRT_Captions.en_US.vtt [1.6 KB] || 14209_Hypermassive_QPO_Simulation_Zoom_YOUTUBE_ProRes_1920x1080_2997.mov (1920x1080) [1.0 GB] || ",
"release_date": "2023-01-09T17:10:00-05:00",
"update_date": "2025-01-12T23:16:27.064142-05:00",
"main_image": {
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"url": "https://svs.gsfc.nasa.gov/vis/a010000/a014200/a014209/Merger_Simulation_Still_1_print.jpg",
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"media_type": "Image",
"alt_text": "Full version of the simulation above, but without labels or other annotations.Credit: NASA's Goddard Space Flight Center and STAG Research Centre/Peter HammondComplete transcript available.",
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{
"id": 13419,
"url": "https://svs.gsfc.nasa.gov/13419/",
"page_type": "Animation",
"title": "NICER Catches Milestone X-ray Burst",
"description": "At about 10:04 p.m. EDT on Aug. 20, NASA’s Neutron star Interior Composition Explorer (NICER) telescope on the International Space Station detected a sudden spike of X-rays caused by a massive thermonuclear flash on the surface of a pulsar, the crushed remains of a star that long ago exploded as a supernova. The X-ray burst, the brightest seen by NICER so far, came from an object named SAX J1808.4-3658, or J1808 for short. The observations reveal many phenomena that have never been seen together in a single burst. In addition, the subsiding fireball briefly brightened again for reasons astronomers cannot yet explain. The data reveal a two-step change in brightness, which scientists think is caused by the ejection of separate layers from the pulsar surface, and other features that will help them decode the physics of these powerful events.The explosion, which astronomers classify as a Type I X-ray burst, released as much energy in 20 seconds as the Sun does in nearly 10 days.J1808 is located about 11,000 light-years away in the constellation Sagittarius, spins at a dizzying 401 rotations each second, and is one member of a binary system. Its companion is a brown dwarf, an object larger than a giant planet yet too small to be a star. A steady stream of hydrogen gas flows from the companion toward the neutron star, and it accumulates in a vast storage structure called an accretion disk.Hydrogen raining onto the pulsar's surface forms a hot, ever-deepening global “sea.” At the base of this layer, temperatures and pressures increase until hydrogen nuclei fuse to form helium nuclei, which produces energy — a process at work in the core of our Sun. The helium settles out and builds up a layer of its own. Eventually, the conditions allow helium nuclei to fuse into carbon. The helium erupts explosively and unleashes a thermonuclear fireball across the entire pulsar surface.As the burst started, NICER data show that its X-ray brightness leveled off for almost a second before increasing again at a slower pace. The researchers interpret this “stall” as the moment when the energy of the blast built up enough to blow the pulsar’s hydrogen layer into space. The fireball continued to build for another two seconds and then reached its peak, blowing off the more massive helium layer. The helium expanded faster, overtook the hydrogen layer before it could dissipate, and then slowed, stopped and settled back down onto the pulsar’s surface. Following this phase, the pulsar briefly brightened again by roughly 20 percent for reasons the team does not yet understand. || ",
"release_date": "2019-11-07T13:00:00-05:00",
"update_date": "2023-05-03T13:45:32.352933-04:00",
"main_image": {
"id": 391439,
"url": "https://svs.gsfc.nasa.gov/vis/a010000/a013400/a013419/nicer_burst_final_still.jpg",
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"media_type": "Image",
"alt_text": "A thermonuclear blast on a pulsar called J1808 resulted in the brightest burst of X-rays seen to date by NASA’s Neutron star Interior Composition Explorer (NICER) telescope. The explosion occurred on Aug. 20, 2019, and released as much energy in 20 seconds as our Sun does in almost 10 days. Watch to see how scientists think this incredible explosion occurred. Credit: NASA's Goddard Space Flight CenterMusic: \"Business As Usual\" from Universal Production MusicComplete transcript available.Watch this video on the NASA Goddard YouTube channel.",
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